We propose to continue our investigations of central neurons responsive to non painful levels of cutaneous cooling, warming, and thermal plus mechanical stimulation as well as neurons activated by noxious levels of thermal stimulation. Details of neuronal response characteristics to standardized sequences of thermal stimuli will be compared at successive synaptic levels. Emphasis will be placed on studies of the trigeminal system in primates and cats. Microelectrode techniques will be used to obtain extracellular recordings from single thermoreceptive neurons located in: a) the spinal nucleus of V, b) thalamus, and c) cerebral cortex. Particular emphasis will be placed on the anatomical localization of thermal neurons and their relationship to patterns of mechanoreceptor (somatic) localization.